1. Chemical Reactions Balance Equation Double-displacement Reaction:  Precipitation  acid-base neutralization  gas-evolving Single-displacement Reaction

2. 22 Experiencing Chemical Change Chemical Reactions: happening both around you and in you all the time! +  some are very simple, others are complex involving changes in the structures of the molecules  many times we can experience the effects of those changes Chemical reactions you experience? Combustion of gasoline/natural gas Seasonal color change of leaves Bleaching of laundry

3. 33 Chemical Reactions Chemical changes: New matter forms Rearrangement and exchange of atoms to produce new molecules Elements are not transmuted A reaction resemble life cyclesA reaction resemble life cycles (at 1:45) Reactants  Products

4. 44 Chemical Equations: Conservation of Mass Matter cannot be created or destroyed Total mass cannot change Total mass of the reactants will be the same as the total mass of the products: Mass Reactant = Mass Product All the atoms present at the beginning are still present at the end: #Atom X (Reactant) = #Atom X (Product) if all the atoms are still there, then the mass will not change

5. 55 Components in Chemical Equations: 2Mg(s) + O 2 (g)  2MgO(s) Shorthand way of describing a reaction Provides information about the reaction Formulas of Reactants (Left) and Products (Right) States of Reactants and Products in “( )”. (solid/liquid/gas) Relative #Reactant and #Product molecules (Coefficients)

6. 6 6 Symbols Used in Equations Indicating the state after chemical (g) = gas; (l) = liquid; (s) = solid (aq) = aqueous = dissolved in water energy symbols used above the arrow for decomposition reactions  = heat h = light shock = mechanical elec = electrical

7. 77 Combustion of Methane: Balanced! To obey the Law of Conservation of Mass, the equation must be balanced CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g) H H C H H + O O C + OO OO + O HH O HH + 1 C + 4 H + 4 O

8. 88 Balance Table For a balanced equation, there are equal numbers of atoms of each element on the Reactant and Product sides to obtain the number of atoms of an element, multiply the subscript by the coefficient 1  C  1 4  H  4 4  O  2 + 2 CH 4 (g) + 2 O 2 (g)  CO 2 (g) + 2 H 2 O(g)

9. 99 How to Write & Balance Chemical Equation 1.Skeletal equation 2.Balance table: Polyatomic ions as one “Group”. 3. Pick an element to balance: Pick Element/Group w/ highest #Atoms 4.Find the Least Common Multiple 5.Multiply each count by a factor to equal the LCM. 6.Recount and Repeat until Balanced. __CH 4 O(g) + __O 2 (g)  __CO 2 (g) + __H 2 O(g)

10. 10 Example Solid aluminum react with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas 1.Write a skeletal equation. 2.Count #Atom or #Groups 3.Setup balancing table and balance. Don’t start with elements in more than one formula 4.Find the Least Common Multiple of the number of atoms on each side.

11. 11 Example Fe(CN) 3 (s) + H 2 SO 4 (aq)  Fe 2 (SO 4 ) 3 (aq) + HCN(aq) ____ and ____ are groups

12. 12 Example: Balance equation C 8 H 18 + O 2  CO 2 + H 2 O

13. 13 Practice: Balancing Equations C 12 H 22 O 11 + O 2  CO 2 + H 2 O (NH 4 ) 3 PO 4 + Ca(NO 2 ) 2  Ca 3 (PO 4 ) 2 + NH 4 NO 2

14. 14 Classifying Reactions A. based on the process that happens (we observes) precipitation, neutralization, formation of a gas, or transfer of electrons

15. 15 Classifying Reactions B. by what the atoms and/or ions do (at molecular/atomic level) Type of ReactionGeneral Equation Synthesis A + B  AB Decomposition AB  A + B Displacement A + BC  AC + B Double Displacement AB + CD  AD + CB

16. 16 Predicting Whether a Reaction Will Occur in Aqueous Solution “Forces” that drive a reaction 1)formation of a solid (aka “Precipitation”) 2)formation of water 3)formation of a gas 4)transfer of electrons when chemicals (dissolved in water) are mixed and one of these 4 things can occur, the reaction will generally happen

17. 17 Double Displacement Reactions Exchange ionic partners: AB + CD  AD + CB Example: Iron(III) nitrate + sodium sulfide  ____________________ + _________________ Double displacement reaction occurs when forming Precipitation Water (Acid-base neutralization reaction) Gas (one of the products to make a gas)

18. 18 Reactions in Aqueous Solutions Often the chemicals we are reacting together are dissolved in water Aqueous solutions = mixtures of a chemical dissolved in water Dissolving the chemicals in water helps them to react together faster Water molecules separate the chemicals into individual molecules or ions The free floating particles collide more frequently so the reaction speeds up

19. 19 Dissociation of Ionic Compound Dissociation: When ionic compounds dissolve in water, the anions and cations are separated from each other - however not all ionic compounds are soluble in water!issociation When compounds containing polyatomic ions dissociate, the polyatomic group stays together as one ion polyatomic ions

20. 20 Dissociation of Ionic Compounds Potassium iodide  potassium cations and iodide anions:KI(aq)  K + (aq) + I - (aq) Copper(II) sulfate  copper(II) cations and sulfate anions: CuSO 4 (aq)  Cu 2+ (aq) + SO 4 2- (aq) K+K+ I-I- K I Cu 2+ SO 4 2- Cu SO 4

21. 21 Polyatomic Ionic Compounds Ammonium sulfate  ammonium cations and sulfate anions (NH 4 ) 2 SO 4 (aq)  2 NH 4 + (aq) + SO 4 2- (aq) SO 4 2- NH 4 + SO 4 NH 4 +

22. 22 Practice: How Ionic Compounds Dissociate? Ammonium phosphate Cobalt(III) sulfate Zinc bromide

23. 23 Formation of Precipitation Depends on the Solubility of Ionic Compound a compound is soluble in a liquid if it dissolves in that liquid. It almost completely dissociate into ions. NaCl is soluble in water a compound is insoluble if a significant amount does NOT dissolve in that liquid. It essentially does NOT dissociate into ions. CaCO 3 (marble stone) is insoluble in water  though there is a very small amount dissolved, but not enough to be significant

24. 24 How to Predict the Solubility of Ionic Compound? Predicting whether a compound will dissolve in water is not easy Such knowledge comes through Experimentation: Do some Experiments to test whether a compound will dissolve in water Then develop some rules based on those experimental results we call this method the Empirical method

25. 25 Compounds Containing the following Ions are Generally Soluble Exceptions (insoluble when combined with ions on the left) Li +, Na +, K +, NH 4 + ; H + ( most acids in this class ) none NO 3 –, C 2 H 3 O 2 –, ClO 4 – None Cl –, Br –, I – Cu +, Ag +, Hg 2 2+, Pb 2+ (CISMILE ) SO 4 2– Ag +, Ca 2+, Sr 2+, Ba 2+, Pb 2+ Solubility Rule. Part I Compounds that are Generally Soluble in Water

26. 26 Compounds Containing the following Ions are Generally Insoluble Exceptions (when combined with ions on the left the compound is soluble or slightly soluble) OH – (hydroxide, base)Li +, Na +, K +, NH 4 +, Ca 2+, Sr 2+, Ba 2+ S 2– (sulfide)Li +, Na +, K +, NH 4 +, Ca 2+, Sr 2+, Ba 2+ Solubility Rule II Compounds that are Generally Insoluble

27. 27 How to predict the solubility of an ionic compound using the previous table? Knowing how to use that table ALONE is generally sufficient to predict the solubility of ionic compound. Rule of Thumb: if the ionic compound of interest does NOT contain any of the listed ions, it is INSOLUBLE! Example: Ca 3 (PO 4 ) 2 if the ionic compound of interest contains BOTH the listed anion AND the cation as EXCEPTION, it is INSOLUBLE. Example: Hg 2 I 2

28. 28 Predict an Ionic Compound’s Solubility in Water: HgSO 4 1. Check the cation: Is it Li +, Na +, K +, or NH 4 + ? If YES  the compound will be soluble in water regardless of the anion! If NO  follow the rule for the anion (Table 7.2) 2. if a rule says the compounds are mostly soluble, then the exceptions are insoluble 3. but if a rule says the compounds are mostly insoluble, then the exceptions are soluble 1.note: slightly soluble  insoluble

29. 29 Practice: Determine if the Following is Soluble in Water Mg(OH) 2 FeCl 3 Pb(C 2 H 3 O 2 ) 2 BaSO 4 (NH 4 ) 3 PO 4 Generally Soluble Exceptions Li +, Na +, K +, NH 4 + ; H + none NO 3 –, C 2 H 3 O 2 –, ClO 4 – None Cl –, Br –, I – CISMILE SO 4 2– Ag +, Ca 2+, Sr 2+, Ba 2+, Pb 2+

30. 30 Insoluble Ionic Compounds do not Dissociate into Ions Insoluble Ionic compounds do not dissolve in water because the Coulombic force among the ions is too strong for water molecules to break down the compound. Therefore they do not dissociate into ions BaSO 4 (s)  Ba 2+ (aq) + SO 4 2- (aq)

31. 31 Precipitation Reactions When two soluble ionic compounds in aqueous solution mix, ion exchange will take place AB + CD  AC + DB if one of the products is insoluble in water, it will come out of solution as a precipitate

32. 32 Precipitation Reactions The “Yellow Tornado”: http://www.youtube.com/watch?v=RE-dFN7U91M&feature=related Pb(NO 3 ) 2 (aq) + 2 KI(aq)  2 KNO 3 (aq) + PbI 2 (s)

33. 33 No Precipitate Formation = No Reaction KI(aq) + NaCl(aq)  KCl(aq) + NaI(aq) all ions still present (all products are soluble),  no reaction

34. 34 Example: When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms 1.Write the formulas of the reactants 2.Determine the ions present for each reactant 4.Exchange the Ions 5.Write the formulas of the products cross charges and reduce Balance the Equation 6.Determine the solubility of each product 7.Add “(s)” after the insoluble products and “(aq)” after the soluble products

35. 35 Practice: Predict whether the following reactions will form precipitate (hint: predict the solubility of each product) BaBr 2 + Na 2 SO 4  BaSO 4 + NaBr (NH 4 ) 3 PO 4 + Ca(NO 3 ) 2  Ca 3 (PO 4 ) 2 + NH 4 NO 3 2HNO 3 + Ca(OH) 2  Ca(NO 3 ) 2 + 2 H 2 O 2 NaOH + CuSO 4  Cu(OH) 2 + Na 2 SO 4

36. 36 Acid-Base Reactions Also as Neutralization reactions : the Acid and Base neutralize each other’s properties H + from the Acid + OH - from the base  Water Cation from the base + Anion from the acid  salt (spectator ions) Acid + Base  Salt + Water 2 HNO 3 (aq) + Ca(OH) 2 (aq)  Ca(NO 3 ) 2 (aq) + 2 H 2 O(l)

37. 37 Example:- Write and Balance equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide 1.Write the formulas of the reactants 2.Determine the ions present for each reactant 3.Exchange the ions, H + combines with OH - to make H 2 O(l). Tip: write water as HOH 4.Write the formulas of the products 5.Balance the Equation ( may be quickly balanced by matching the numbers of H and OH to make HOH) 6.Determine the solubility of the salt 7.Write an (s) after the insoluble products and a (aq) after the soluble products

38. 38 Gas-Evolving Reactions Some reactions form a gas directly From the ion exchange K 2 S(aq) + H 2 SO 4 (aq)  K 2 SO 4 (aq) + H 2 S(g) Other reactions form a gas by the decomposition of one of the products into a gas and water Step 1: Na 2 CO 3 (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 CO 3 (aq) Step 2: H 2 CO 3  H 2 O(l) + CO 2 (g) Overall reaction: Na 2 CO 3 (aq) + H 2 SO 4 (aq)  Na 2 SO 4 (aq) + H 2 O(l) + CO 2 (g)

39. 39 Compounds that Undergo Gas Evolving Reactions Reactant Type Reacting With Ion Exchange Product Decom pose? Gas Formed Example metal n S, metal HS acid H2SH2S no H2SH2S K 2 S(aq) + 2HCl(aq)  2KCl(aq) + H 2 S(g) metal n CO 3, metal HCO 3 acid H 2 CO 3 yes CO 2 K 2 CO 3 (aq) + 2HCl(aq)  2KCl(aq) + CO 2 (g) + H 2 O(l) metal n SO 3 metal HSO 3 acid H 2 SO 3 yes SO 2 K 2 SO 3 (aq) + 2HCl(aq)  2KCl(aq) + SO 2 (g) + H 2 O(l) (NH 4 ) n anionbase NH 4 OH yes NH 3 KOH(aq) + NH 4 Cl(aq)  KCl(aq) + NH 3 (g) + H 2 O(l)

40. 40 Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves 1.Write the formulas of the reactants 2.Determine the ions present when each reactant dissociates 3.Exchange the Ions 4.Write the formulas of the products 5.Check to see either product H 2 S, or if either product decomposes into gas (H 2 CO 3, H 2 SO 3, NH 4 OH) 6.Balance the Equation 8.Determine the solubility of other product 9.Write “(s)”, or “(aq)”, or “(l) for water, or “(g)” for each product if appropriate

41. 41 Practice: Complete and Balance the following double- displacement Reactions; Predict whether the following reactions will form precipitate, gas, or neutralization (hint: predict the solubility of each compound) Pb(C 2 H 3 O 2 ) 2 + Na 2 SO 3  NH 4 OH + Fe(NO 3 ) 2  HNO 3 + Al(OH) 3  HCl + (NH 4 ) 2 CO 3  Ba(OH) 2 + (NH 4 ) 2 CO 3 

42. 42 Beyond Double Displacement Rxns Precipitation, Acid-Base, and Gas-evolving reactions all involved exchanging the ions in the solution Oxidation-Reduction reactions : reactions involve transferring electrons from one atom to another – also known as redox reactions many of these reactions are not done by dissolving the reactants in water Examples: Reaction between elements, Single Displacement Reaction, Combustion Reaction

43. 43 Reactions of Metals with Nonmetals Reactions of Metals with Nonmetals (Oxidation-Reduction) metals react with nonmetals to form ionic compounds ionic compounds are solids at room temperature the metal loses electrons and becomes a cation the metal undergoes oxidation: Na  Na + + e - the nonmetal gains electrons and becomes an anion the nonmetal undergoes reduction: Cl 2 + 2e -  2 Cl - Overall Reaction: 2 Na(s) + Cl 2 (g)  2NaCl(s)

44. Single-Replacement Reactions Aka Single-Displacement Reaction: A reaction in which a more active element displaces another less active element in a compound. A + BC  AB + C When iron bar placed in copper(II) sulfate solution: Iron is corroded, copper metal appears, blue color (Cu 2+ ion) fades. Fe(s) + CuSO 4 (aq) → FeSO 4 (aq) + Cu(s) Here ______ is more active than ____.

45. 45 Single Displacement Reactions Active Metal replaces Hydrogen: 2Na(s) + 2H 2 O(l)  2NaOH(aq) + H 2 (g) Zn(s) + 2 HCl(aq)  ZnCl 2 (aq) + H 2 (g) Active Metal replaces Less Active Metal: Fe 2 O 3 (s) + 2Al(s)  Al 2 O 3 (s) + 2Fe(s) Active nonmetal displaces Less Active nonmental: Cl 2 (g) + 2 KI(aq)  2 KCl(aq) + I 2 (s) F 2 (g) + 2H 2 O(l)  O 2 (g) + 4HF(aq)

46. Predicting Single Replacement Reactions: Activity Series Metals that are most reactive appear first in the activity series. The relative activity series (decreasing activity): H Li > K > Ba > Ca > Na > Mg > Al > Mn > Zn > Fe > Cd > Co > Ni > Sn > Pb > (H) > Cu > Ag > Hg > Au High activity Element will replace Low Activity Element (HELC): 2Na + 2H 2 O  2NaOH + H 2

47. Aqueous Acid Displacements Metals that precede (H) in the activity series react with acids, and those that follow (H) do not react with acids. More active metals react with acid to produce hydrogen gas and an ionic compound. Fe(s) + 2 HCl(aq) → FeCl 2 (aq) + H 2 (g) Metals less active than (H) show no reaction. Au(s) + H 2 SO 4 (aq) → NR

48. Active Metals and Water A few metals are active enough to react directly with water. These are called active metals. They react with water to produce a metal hydroxide and hydrogen gas. 2 Na(s) + 2 H 2 O(l) → 2 NaOH(aq) + H 2 (g) Ca(s) + 2 H 2 O(l) → Ca(OH) 2 (aq) + H 2 (g)

49. 49 Practice: A student placed zinc metal in the solution containing Mg 2+, Cu 2+ and Ag + ions, predict if single replacement rxn will occur and what the product will be H Li > K > Ba > Sr > Ca > Na > Mg > Al > Mn > Zn > Fe > Cd > Co > Ni > Sn > Pb > (H) > Cu > Ag > Hg > Au

50. 50 Combustion Reactions Reactions in which O 2 (g) is a reactant are called Combustion Reactions Combustion reactions release lots of energy Combustion reactions are a subclass of Oxidation- Reduction reactions 2 C 8 H 18 (g) + 25 O 2 (g)  16 CO 2 (g) + 18 H 2 O(g)

51. 51Tro's Introductory Chemistry, Chapter 7 Combustion Products to predict the products of a combustion reaction, combine each element in the other reactant with oxygen ReactantCombustion Product contains CCO 2 (g) contains HH 2 O(g) contains SSO 2 (g) contains NNO(g) or NO 2 (g) contains metalM 2 O n (s)

52. 52Tro's Introductory Chemistry, Chapter 7 Combination Reactions also known as Composition or Synthesis reactions Two (or more) reactants combine together to make one product simpler substances combining together 2 CO + O 2  2 CO 2 CaO + H 2 O  Ca(OH) 2 2H 2 + O 2  2H 2 O

53. 53Tro's Introductory Chemistry, Chapter 7 Decomposition Reactions ONE large molecule is broken apart into smaller molecules or its elements caused by addition of energy into the molecule From one reactant, make 2 or more products

54. 54 Practice: Write and Balance Word Equations iron(III) chloride + copper metal  iron(II) chloride + copper(II) chloride nitrogen gas + magnesium metal  magnesium nitride zinc phosphate + hydrochloric acid  phosphoric acid + zinc chloride acetic acid + oxygen gas  carbon dioxide + water

55. 55 Determine if Each of the Following is Soluble in Water KOHSoluble, because the cation is K + AgBrInsoluble, even though most compounds with Br - are soluble, this is an exception CaCl 2 Soluble, most compounds with Cl - are soluble Pb(NO 3 ) 2 Soluble, because the anion is NO 3 - SrSO 4 Insoluble, even though most compounds with SO 4 2- are soluble, this is an exception

56. 56 Example: When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms 1.Write the formulas of the reactants Na 2 CO 3 (aq) + CuCl 2 (aq)  2.Determine the ions present when each reactant dissociates (Na + + CO 3 2- ) + (Cu 2+ + Cl - )  3.Exchange the Ions (Na + + CO 3 2- ) + (Cu 2+ + Cl - )  (Na + + Cl - ) + (Cu 2+ + CO 3 2- )

57. 57 4.Write the formulas of the products cross charges and reduce Na 2 CO 3 (aq) + CuCl 2 (aq)  NaCl + CuCO 3 5.Balance the Equation Na 2 CO 3 (aq) + CuCl 2 (aq)  NaCl + CuCO 3 Example: When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms

58. 58 6.Determine the solubility of each product NaCl is soluble CuCO 3 is insoluble 7.Write an (s) after the insoluble products and a (aq) after the soluble products Na 2 CO 3 (aq) + CuCl 2 (aq)  NaCl(aq) + CuCO 3 (s) Example - When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms

59. 59 Example:- Write and Balance equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide 1.Write the formulas of the reactants HNO 3 (aq) + Ca(OH) 2 (aq)  2.Determine the ions present when each reactant dissociates (H + + NO 3 - ) + (Ca 2+ + OH - )  3.Exchange the ions, H + combines with OH - to make H 2 O(l). Tip: write water as HOH (H + + NO 3 - ) + (Ca 2+ + OH - )  (Ca 2+ + NO 3 - ) + HOH(l)

60. 60 4.Write the formulas of the products cross charges and reduce HNO 3 (aq) + Ca(OH) 2 (aq)  Ca(NO 3 ) 2 + HOH(l) 5.Balance the Equation may be quickly balanced by matching the numbers of H and OH to make HOH coefficient of the salt is always 1 2 HNO 3 (aq) + Ca(OH) 2 (aq)  Ca(NO 3 ) 2 + 2 HOH(l) Example: Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

61. 61 6.Determine the solubility of the salt Ca(NO 3 ) 2 is soluble 7.Write an (s) after the insoluble products and a (aq) after the soluble products 2 HNO 3 (aq) + Ca(OH) 2 (aq)  Ca(NO 3 ) 2 (aq) + 2 H 2 O(l) Example 7.11 - Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

62. 62 Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves 1.Write the formulas of the reactants Na 2 SO 3 (aq) + HNO 3 (aq)  2.Determine the ions present when each reactant dissociates (Na + + SO 3 2- ) + (H + + NO 3 - )  3.Exchange the Ions (Na + + SO 3 - ) + (H + + NO 3 - )  (Na + + NO 3 - ) + (H + + SO 3 2- )

63. 63 4.Write the formulas of the products cross charges and reduce Na 2 SO 3 (aq) + HNO 3 (aq)  NaNO 3 + H 2 SO 3 5.Check to see either product H 2 S - No 6.Check to see of either product decomposes – Yes H 2 SO 3 decomposes into SO 2 (g) + H 2 O(l) Na 2 SO 3 (aq) + HNO 3 (aq)  NaNO 3 + SO 2 (g) + H 2 O(l) Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves

64. 64 7.Balance the Equation Na 2 SO 3 (aq) + 2 HNO 3 (aq)  NaNO 3 + SO 2 (g) + H 2 O(l) 8.Determine the solubility of other product NaNO 3 is soluble 9.Write an (s) after the insoluble products and a (aq) after the soluble products Na 2 SO 3 (aq) + 2 HNO 3 (aq)  NaNO 3 (aq) + SO 2 (g) + H 2 O(l) Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves

65. 65 Practice: Complete and Balance the following Word equations copper(II) nitrate + sodium carbonate silver acetate + ammonium chloride potassium carbonate + phosphoric acid barium hydroxide + sulfuric acid

66. 66 Practice: Complete and Balance the following Word equations copper(II) nitrate + sodium carbonate silver acetate + ammonium chloride potassium carbonate + phosphoric acid barium hydroxide + sulfuric acid Cu(NO 3 ) 2 (aq) + Na 2 CO 3 (aq)  NaNO 3 (aq) + CuCO 3 (s) AgC 2 H 3 O 2 (aq) + NH 4 Cl(aq)  AgCl(s) + NH 4 C 2 H 3 O 2 (aq) 3K 2 CO 3 (aq) + 2H 3 PO 4 (aq)  2K 3 PO 4 (aq) + 3H 2 O(l) + 3CO 2 (g) Ba(OH) 2 (aq) + H 2 SO 4 (aq)  BaSO 4 (s) + 2 H 2 O(l)